1. Field of the Invention
This invention relates to yeast extracts. In particular, this invention relates to yeast extracts having novel and interesting flavors which are produced by the modification of conventional processes for producing yeast extract.
2. Description of Related Art
Yeast extract is a nutritious palatable paste prepared from brewer's or baker's yeast by autolysis. This process comprises the self-digestion of yeast cells principally through yeast proteolytic enzyme activity so that proteinaceous soluble solids can be recovered and, if desired, concentrated to form a paste.
In conventional processes, yeast is diluted with water to a specified solids content before autolysis. Salt may be added to the resulting slurry to aid cell membrane rupture and to exercise a degree of control over microbial flora. Yeast proteins are solubilized and hydrolysed during the autolysis process. Although the natural yeast enzymes may be sufficient to carry out the hydrolysis, the activity of the yeast proteolytic system may optionally be augmented by the addition of exogenous enzymes.
On completion of the autolytic process, the soluble fraction is harvested and concentrated by a series of evaporation steps to give a typical standard yeast extract. The autolytic process typically solubilizes around 62% of the starting total yeast solids and yields a maximum of 80% of the yeast's original protein content.
WO 91/16447 discloses a process for producing yeast extracts in which the autolysis process is carried out on a mixture of yeast and non-yeast protein source such as gluten, bran or soya bean meal. The process relies upon the yeast proteolytic system or an exogenous proteolytic enzyme to break down the non-yeast protein source.
U.S. Pat. No. 4,194,017 describes the production of meat flavored products by the steam distillation of treated yeast extract and the reaction of the residue following distillation with a vegetable protein hydrolysate, a monosaccharide and a sulphur-containing substance. The resulting product is claimed to be free from any aftertaste from either the yeast extract or the hydrolysate.
JP 72-03142 teaches a method for eliminating yeast and amino acid odors from yeast extract by heating the extract in the presence of enzymatically hydrolysed vegetable protein.
It has now been found that a range of yeast extract-based products having a variety of novel and interesting flavors may be produced which, as a result of the diversity of their flavors, have many potential applications in areas where the use of conventional yeast extracts is inappropriate. Since yeast extract is highly nutritious, the ability to tailor its taste to suit different requirements or personal preferences either as an additive to other foodstuffs or as a product per se is highly beneficial.
This invention allows the production of flavored yeast extracts by the use of naturally occurring plant or fungal material by modification of the conventional yeast autolysis process.